1. Field of the Invention
The present invention relates to a device for maintaining a partial opening of the throttle during deceleration for carburetors of clean-burning internal combustion engines.
2. Description of the Prior Art
Known carburetors generally have a device called a "throttle opener" which, when one ceases accelerating in starting up a vehicle, thus reclosing the throttle, again partially opens this throttle in order to avoid too great a vacuum in the induction pipe which would result in draining the idling passage and drying up the fuel supply for filling it. The consequence of this situation is to allow the escape of unburned hydrocarbons and produce too lean a mixture in the motor, as well as hesitations in reaccelerating, part of the fuel being taken up in repriming the circuits and refilling the passages previously drained.
These throttle-partial opening devices generally consist of a capsule with a diaphragm connected to the induction pipe downstream of the carburetor throttle. The vacuum in the pipe acts on the diaphragm, which in turn opens the throttle, thus correcting the vacuum, on the one hand, and permitting, on the other, the admission to the motor of a mixture sufficiently rich for combustion and not producing unburned hydrocarbons in the exhaust.
These devices, however, lack sensitivity and do not give complete satisfaction. In particular, at the moment of lifting the foot from the accelerator, they do not prevent complete closure of the throttle, causing the vacuum necessary to reopen it and thus the production of unburned hydrocarbons during this period. Likewise, at the end of a period of deceleration, the corresponding decrease in vacuum in the pipe causes the premature closure of the throttle to the idling position and production of unburned hydrocarbons.